Method and composition for improving diesel fuel ignition



Patented May 14, 1940 UNITED STATES METHOD AND COMPOSITION FOR IMPROV- ING DIESEL FUEL IGNITION Alvin A. Burton, Albany,

Calif., assignor to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware No Drawing. Application May 1, 1939, Serial No. 271,169.

12 Claims.

This invention relates to fuels for internal combustion engines of the Diesel type, and it has particularly to do with the addition to liquid petroleum fuels of substances designed to control the combustion characteristics of the fuels and their tendency to deposit carbon or carbonaceous material in the combustion chamber in which they are exploded. a

In Diesel engine operation, a liquid fuel is injected into a combustion chamber and ignited by compressiom In the attainment of minimum knocking, the time interval'between the instant of injection and the instant of ignition, referred to as the "delay period, should be as brief as possible. Generally this delay period is known to be affected by the type or character of the hy-- drocarbons composing the fuel; also, it may be shortened by the addition of ignition accelerators or primers to the fuel, and various substances are known to be effective for this purpose. Occasionally, but not invariably, the addition of a substance found to act as an efllcient primer during continuous running will also act to assist in the cold starting of the motor. Infrequently,

a substance found to act as an eillcient primer will assist in decreasing carbon deposition on the injection nozzle.

It has been found that the addition of'small amounts of chloropierin to a Diesel fuel shortens the period of delay between injection and ignition, enables the motor to be started at a considerably lower temperature, under its own compression, and prevents the deposition of carbon or carbonaceous material in the combustion chamber, particularly on injection nozzles and exhaust valves, where carbon deposition adversely affects motor emciency. When admixed with a Diesel fuel in requisite small amounts, the fuel is non-explosive under ordinary storage 'conditions and its manufacture and storage is atof chloropicrin. It is another object of the invention to disclose Diesel fuels of enhanced combustion characteristics, capable of smooth operation at minimum knocking and with minimum delay periods, which are low in cost, stable in storage and without undue hazard in preparation or handling. It is another object to provide methods of utilizing chloropicrin in the cold starting of Diesel motors by providing for the introduction to the motor of higher concentrations of chloropicrin than suffice for highly efli- I i cient continuous running. Other objects, uses and advantages of the invention will be apparent to those skilled in the art to which it appertains.

The chloropicrin which is added to a Diesel 1 type hydrocarbon fuel for the purposes of the invention is nitrotrichlormethane, nitrochloroform or, more familiarly, chlorpicrin. Structurally, it is represented thus:

By the addition of chloropicrin to a Diesel type fuel, in an amount between about 0.2% and about 20 I number" rise being indicative of a decrease in de- 25 lay period between in'jectionand ignition in the motor combustion chamber, as exemplified in the following:

Cetane number rise 0 Cetane Cetane num- Fuel number berincreose Petroleum Diesel fuel 39 I v Petroleum Diesel run-4mg chloropicrim. 4a 4 Petroleum Diesel fuel- -0.25 o chloro icrin. 46 7 Petroleum Diesel [nob-0.6 chlorop crin.- 49 i0 Petroleum Diesel fuel- -1. chloropicrlm. 54 15 Petroleum Diesel fuel--2. chloropicrin -57 l8 Petroleum Diesel iuel-5. chloropicrin. 73 34 The above additions vof chloropicrin were all made to the same base Diesel fuel, and the determinations of cetane number were all made in the same standardized engine under closely controlled and' accurately duplicable conditions.

The cetane number determinations given herein are determined by 'a procedure known as the Standard Oil Company of California delay meth- 0d, in which the ignition delay with combustion occurring at top dead center is utilized as the test 50 criterion and in'which the operating variable is the injection advance equivalentto the ignition delay when firing is made to occur at top dead; center. In brieffthis procedure is characterized! as follows: The fuel to be tested is introduced into the engine and the injection is then advanced or retarded until firing occurs at top center; the ignition delay is read and recorded. The procedure is then repeated for a series of cetanealphamethylnaphthalene blends which produce greater and lesser ignition delaysthan the fuel under test. A plot is made of the ignition delays of the cetane-alphamethylnaphthalene blends in terms of the percentage of cetane in the blends. The ignition delay of the fuel under test is placed on this plot and its corresponding cetane number is determined. The method may be employed in a Fairbanks Morse or other service engine capable of sufficient control of all operation variables. The method correlates well with service performance.

By the addition of chloropicrin to Diesel type fuels in the amounts already referred to, carbonor carbonaceous-deposits in the motor combustion chamber are materially reduced in quantity, as exemplified by the following, taken from a pair of duplicate test runs in the same standard engine under the same test conditions:.

Carbon deposition-combustion chamber In these tests, the engine employed was a direct injection, 1000 R. P. M., 12 to 1 compression ratio, full Diesel engine; the test conditions were 150 F.

jacket temperature, 100 F. air intake tempera.- ture, 800 R. P. M. idle load, engine intake air throttled equivalent to 5000 feet elevation, therea by tending to accelerate engine deposits. This set of accelerating test conditions has been found to correlate with service conditions in carbonand carbonaceous-deposition.

Further, the presence of chloropicrin in Diesel fuels is of advantage in the cold starting of Diesel motors.

Generally, under given conditions of starting, the minimum temperature at which the engine will fire and continue to operate, on an uncompounded petroleum hydrocarbon fuel, depends upon the delay cetane number of the fuel, and it is lowered relative to a rise in delay cetane number. It has been found that the presence of the chloropicrin of this invention in a hydrocarbon fuel of the Diesel type causes a lowering in the temperature of cold starting, in degrees Fahrenheit, about equivalent to the cetane number rise caused by their presence. Such an effect is by no means generally true of substances found to cause cetane number rise upon addition to hydrocarbon fuels: for'example, ethyl nitrate, effective to cause cetane number rise, causes little or no lowering of the temperature of cold starting when added to and introduced in a fuel to the extent of 1-5% by weight. I

The procedure employed in determining the starting qualities of the Diesel fuels of this in vention, exemplified above as causing a lowering in temperature of cold starting, in degrees Fahrenheit, about equivalent to cetane number rise brought about by chloropicrin addition, is referred to as the Standard Oil Company of California cold starting method, and utilizes the ambient temperature allowing a starting just 5 seconds subsequent to initial cranking as the test criterion. In brief, this procedure is characteraeoaaeo raised or lowered as required to result in starting with just 5 seconds of cranking. This final temperature is recorded as the ambient starting temperature of the fuel. A Caterpillar engine is em-= ployed under service conditions, and the starting temperature determinations are representative of field performance.

Thus a certain unblended Diesel distillate fuel, containing no primer, would not allow the test engine to start at temperatures below 59 F. The addition of 2.0% of chloropicrin to this fuel ai lowed the engine to start at 47 F. In the absence of any primer or additive ignition accelerating agent, a hydrocarbon fuel would require a cetane nun ber (by the above-described delay method) of. 58 in order that this engine might be started at a temperature as low as 47 F.

Under certain more unusual conditions, for example in cold starting at very low temperatures,

in accelerating starting at ordinary temperatures, and in operations with hydrocarbon fuels of low cetane number, it has been found advantageous to introduce more than the already disclosed small amounts of chloropicrin (based on the hydrocarbon fuel components), sometimes for brief periods only. This may be done by controlled introduction of the chloropicrin to the air intake manifold or stream to the motor, either with or without the presence of the usual small amounts of chloropicrin in the fuel introduced in the liquid injection system. Such air intake introduction obviates the difficulty of purging the regular fuel system and provides for discontinuous addition for special sets of circumstances. .It may be accomplished by addition of the chloropicrin through a short section of the intake pipe, arranged on a by-pass as desirable, containing loosely packed copper or other suitable metal wool, from a liquid flow line appropriately calibrated or supplied from a-chamber with suitable calibration.

' By reason of the low boiling point of chloropicrin and because of its peculiarly objectionable physiological and chemical properties when handled alone, and also because of the advantages flowing from accurate measurement of the quantities introduced, it is preferable to supply to the air intake stream a solution or suspension of the :chloropicrin rather than the substance itself:

mixtures containing 10% or more by weight of chloropicrin, in a hydrocarbon fuel of the gasoline or Diesel fuel boiling range or a combustible or noncombustible liquid such as carbon tetrachloride or chloroform, an alcohol such as methyl,, ethyl, isopropyl or a higher alcohol or ether, or

mixtures of such alcohols and/or ethers, are suitable for this purpose; a mixture of 10% up to 50 or more per cent of chloropicrin in the Diesel fuel ordinarily employed in the continuous running of the motor is particularly advantageous.

For example, inthe cold starting method referred to, an unblended hyrocarbon 40 cetane.

number fuel allowed the test motor to start in 5 seconds at a temperature of 59 F. The introduction of 20 milliliters of chloropicrin to the air intake manifold in the manner described allowed the test engine to start in seconds at a temperature of 20 F. In this engine, a 100 cetane number fuel is required for a 5 second start at 20 F. During the 5-second starting operation, but 1 milliliter of liquid fuel was introduced through the fuel injection nozzles, hence it will be seen that the ratio of chloropicrin to hydrocarbon fuel in this starting operation was 20:1. Ratios as high as' 50:1 and as low as 1:20 may be employed in operations of this character. Discontinuous additions at other than starting times may occasionally be of advantage with this air intake method of introduction.

The addition of chloropicrin to other base Diesel fuels than those exemplified hereinabove brings into being efl'ects comparable to those as exemplified.

The term Diesel fuel as used herein has particular reference to petroleum distillates of kerosene and light gas oil boiling range, but the tem is intended to include as well both the slightly more and the slightly less volatile dis tillates which are designed for ordinary use in internal combustion engines of the Diesel type.

I claim:

1. An improved Diesel fuel comprising a hydrocarbon fuel oil containing between about 0.1% and about 10.0% by weight of chloropicrin.

2. An improved Diesel fuel comprising a hydrocarbon fuel oil containing between about 0.5% and about 2.0% by weight of chloropicrin. 3. An improved Diesel fuel comprising a-hydrocarbon fuel oil containing about 1.0% by weight of chloropicrin. I

4. An improved Diesel fuel consisting of a hydrocarbon fuel oil containing betweenabout 0.1% and about 2.0% by weight of chloropicrin.

5. An improved Diesel fuel comprising a hydrocarbon fuel oil containing a minor proportion of chloropicrin, sumcient to decrease the ignition delay period of the fuel, improve its cold starting ability and decrease its tendency to deposit carbon and carbonaceous material in the motor combustion chamber.

'6. An improved Diesel engine ignition accelerating composition comprising chloropicrin in admixture with a liquid diluent, the said composition containing at least 0.1% of chloropicrin by weight.

'7. An improved Diesel engine ignition accelerating composition comprising chloropicrin in admixture with a liquid diluent, the said composition containing at least by weight of chloropicrin.

8. An improved Diesel engine ignition accelerating composition comprising chloropicrin in admixture with a liquid diluent. the said composition containing more than 50% by weight of chloropicrin.

9. The method of accelerating the ignition of Diesel cycle internal combustion engines which comprises admixing with the fuel, prior to ignition, a minor proportion of chloropicrin.

10. The method of accelerating the ignition of a Diesel cycle internal combustion engine which comprises introducing chloropicrin to the combustion chamber of the engine, simultaneously with the introduction thereto of a hydrocarbon Diesel fuel.

11. The method of accelerating the ignition a: a Diesel cycle internal combustion engine which comprises introducing chloropicrin to the air intake manifold of the engine, simultaneously with the introduction of a hydocarb'on Diesel fuel to the combustion chamber of the said engine.

12. The method of accelerating the ignition of a" Diesel cycle internal combustion engine which "comprises introducing chloropicrin in a diluent to the air intake manifold of the engine, simultaneously with the introduction of a hydrocarbon Diesel fuel to. the combustion chamber-of the said engine.

ALVIN A. BURTON.

DISCLAIMER 2,200,260.Al"vin A. Burton, Albany, Calif. METHOD AND Comosrnon FOR Immov- ING DIESEL FUEL IGNITION. Patent dated May 14, 1940. Disclaimer filed August 26, 1941, by the assignee, Standard Oil Company of Oalz'form'a.

Hereby enters this disclaimer to claims 3, 5, 9, and 10 of said Letters Paent.

[Oyfioz'al Gazette September 16, 1.941.] 

